between the routine communication and the descent. why was there no distress call from the cockpit in. >> i think they were incapacitated or for some reason to respond and control the plane. for what the plane did in the final few minutes, i don't think a conscious pilot was doing it. >> reporter: what could have caused the pilots to lose consciousness? two of the theory rapid decompression or a fire in the cockpit. one official speaking to the new york times refuses to rule out terrorism saying we don't have any evidence that points to a technical explanation. we have to consider the possibility of deliberate human responsibility. another said it's not considered the most likely explanation for the wreck. a little more than 60 years ago another airliner crashed into these alps killing all on board.